the other frequently varient of the query i will be using is
SELECT topicId, topicName, creatorId, createdBy, creatorClass, UNIX_TIMESTAMP(createdAt) as createdAt, creatorIP, totalPosts, lastPosterId, lastPoster, lastPosterClass, UNIX_TIMESTAMP(lastPostTime) as lastPostTime, lastPosterIP, is_pinned FROM PUBLICFORUM.tbl_topic FORCE INDEX (is_pinned) WHERE topicStatus = 'active' and forumId = 1 and is_deleted = 0 and ( accessLevel<=0 OR ( accessLevel=1 and topicId in (1, 2) ) ) ORDER BY is_pinned, lastPostTime

and in the 2nd query the list of topicId in the in expression at end can increase many folds